This Program Project application proposes a diverse yet highly integrated program that investigates fundamental mechanisms of cell signaling and cell death in brain endothelial cells, neurons, astrocytes and matrix. Our program, reorganized from our last submission, consists of four projects, each of which draws from our strengths at MGH and BWH. We address novel hypotheses that take advantage of new research directions and opportunities to focus on dissecting neurovascular substrates and mechanisms of brain cell and vascular injury after ischemia, as recommended by the NINDS Stroke Program Review Group. Our overall theme focuses on the neurovascular unit. In Project 1 (Moskowitz), we examine the hypothesis that neurovascular coupling via cortical spreading depression triggers matrix metalloproteinase (MMP) disruption of the blood-brain barrier (BBB), that may ultimately contribute to ischemic edema and an accumulating burden of injury in brain regions outside the territory of vascular compromise. Project 2 (Lo) extends this concept by investigating mechanisms of MMP dysregulation, tests the hypothesis that proteolytic disruption of cell-matrix homeostasis initiates anoikis-like death in cells of the neurovascular unit, and examines the modulatory actions of angiotensin and statins. In Project 3 (Liao), we dissect the role of the protein kinase Akt as a cell survival signal in cerebral endothelium and neurons, using novel inducible Akt transgenic mice to examine effects of statins, steroid hormones, and growth factors in the regulation of cerebral blood flow, BBB function and cell death. Finally, Project 4 (Huang) continues our neurovascular theme by using novel transgenic mice to investigate how interactions between ApoE and endothelial NOS mediate endothelial injury and vascular dysfunction in ischemia. Throughout, we will use a multidisciplinary approach, combining tools of molecular and cell biology with in vivo physiology and pharmacology. Each project will be supported by a Scientific Imaging Core (Hyman, Boas) that applies advanced optical, fluorescence and MR imaging techniques for mapping a wide range of functional neurovascular parameters in vivo and an Administrative Core (Moskowitz). Together, the individual projects and Scientific Core form a synergistic series of investigations that are intended to yield novel data and a more advanced understanding of neurovascular dysfunction, as we collectively seek to translate fundamental findings into clinically effective stroke therapies.